We propose to determine portal blood flow by a cannulating electromagnetic flow meter in dogs under chloralose-morphine anesthesia. Simultaneous determinations of the level of serum gastrin by immunoassay will permit us to measure the amount of gastrin released by electrical stimulation of the vagus nerves. This will make it possible to treat our data on gastrin release and acid secretion during vagal stimulation based upon determinations of gastrin concentration on a quantitative basis. We plan to develop a mathematical model from our data and test it by pertubations in vivo such as decerebration, antral perfusions and intestinal perfusions.